Furnace wall construction

ABSTRACT

An efficient and inexpensive wall construction is provided for an electric furnace of the resistance type in which breakage is minimized and parts are easily replaced if breakage does occur. The furnace lining extends over the inside wall of the furnace and includes ceramic panels designed to receive and support electrical resistance elements, such as resistor ribbon or the like. In one form the lining comprises a layer of fibrous ceramic insulating material which is supported on the inside of a furnace outer wall or shell. Headed fastener studs extend through the insulating material and are secured to the furnace shell with their heads spaced therefrom. The ceramic heating element support panels are removably mounted on the fastener studs and held in place by the headed ends thereof. In a preferred form of the construction the ceramic panels are disposed in horizontal rows whereby the panels of one row rest on and are partially supported by the panels of the row below.

United States Patent Hicks 1 1451 Dec. 5, i972 1541 FURNACE WALL CONSTRUCTION [72] Inventor: Gerald W. Hicks, Elyria, Ohio [73] Assignee: Lee Wilson Engineering Company, 7

Inc., Cleveland, Ohio [22] Filed: Sept. 2, 1971 [21] Appl. No.: 177,408

[52] US. Cl. ..l3/20, l3/25, 219/311, 1 219/355, 219/390, 219/406, 219/536,

[511' int. Cl..' ..-.....l'l05b 3/06 1581 Field of Search ..13/20,'22, 25, 31, 35; 219/31 1, 355, 390, 406, 407, 536, 550; 338/3l5,3l6,321

[56] References Cited UNITED STATES PATENTS 1,768,865 7/1930 Smalley.. ..13/2s 3,427,011 2/1969 Boyer et a1. ..13/31 x Primary Examiner-Roy N. Envall, Jr. Att0mey-Paul S. Sessions et al.

[57] ABSTRACT An efficient and inexpensive wall construction is provided for an electric furnace of the resistance type in which breakage is minimized and parts are easily replaced if breakage does occur. The furnace lining extends over theinside wall of the furnace and includes ceramic panels designed to receive and support electrical resistance elements, such as resistor ribbon or the like. In one form the lining comprises a layer of fibrous ceramic insulating material which is supported on the inside of a furnace outer wall or shell. Headed fastener studs extend through the insulating material and are secured to the furnace shell with their heads 1 spaced therefrom. The ceramic heating element support panels areremovably mounted on the fastener studs and held in place by the headed ends thereof. In a preferred form of the construction the Ceramic panels are disposed in horizontal rows whereby the panels of one row rest on and are partially supported by the panels of the row below.

6 Claims, 10 Drawing Figures PATENTED m 5 We SHEET 1 OF 2 2| fizz FIIIIII I A I INVENTOR. GERALD W HICKS zih .ZZ M, M w

ATTORNEYS IP'A'TENTEOMB 5 I912 3.705.253

SHEET 2 0F 2 INVENTOR GERALD W HICKS FURNACE WALL CONSTRUCTION BACKGROUNDOF THE INVENTION In industrial electric furnaces, such as those designed for annealing procedures, heating elements, consisting of ribbons or elongated coils of suitable electrical resistant metal, are commonly 'festooned in vertically spaced rows upon supports which project inwardly from the wall of thefurnace.

The resistance elements used in electric furnaces have a relatively short usefullife due to failure orburning-out of the element, particularly by localized heating. Localized heating may be occasioned by excessive current density, inadequateor improper heat radiation, or by mechanical defects -or weaknesses in the resistance element. Moreover, in use cracking and other breakage of parts occur due to stresses created along the furnace wall by temperature differentials and/or by expansion and contraction of parts as the 'furnacelheats and cools, or'due to still other causes.

Forvarious reasonsfailure of thelheating elements or their supports may occur and, to replace damaged parts,it .is 'necessaryto permit the furnace to cool .so

that workmen may reach the damaged area; This results in expensive down-time for the furnace. Additionally, the labor involved can be fairly time-consuming and expensive so thatfurther economic loss is met in furnacerepair'and'operating time.

I SUMMARY OF THE INVENTION The present lining construction for an electric furnace can be easily, quickly and inexpensively installed. Further, the construction minimizes breakage of parts and, when breakage or other failure does occur,-enables replacements to be readily made.

In one form, the lining comprises a porous, somewhat resilient layer, preferably a ceramic fiber batt, which is laid against the inside of the furnace wall. Headed studs or pins penetrate the fibrous layer and have their penetratingends secured tothe furnace wall as by spot weldingwhile leaving the heads at the opposite ends ofnthe studs sufficientlyspacedfrom theinsulatinglayer toform support means. Ceramic panels, having means to carry electric resistorelements, are removably mounted on the'headed ends of the studs.

In a preferred form, horizontallydisposed rows of the panels are secured against the insulating layer insucha manner that the panels of one row contact adjacent panels of other rows. The panels of a lower row thereby assist in supportingthe panelsof the upper, adjacent row. .The resilient, compressible nature of the fibrous insulating layer permits it toaccommodate'itself to the structural expansions and contractions which are caused by temperature changes, thus relieving forces which otherwise might result in breaking and cracking of parts. Further, if panel breakageshould occur, itisa simple matter to lift the brokenpanel free of its supporting stud heads and mount a-replacement panel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical, cross sectional view of an electric annealing furnace having a lining and thehangerpanels of the present invention;

FIGLZ is a'fragmentary, enlarged vertical cross-sectional view of a portion of the furnace lining of'FIG. l;

to FIG. 4 but illustrating a modified typefof cavity structure for a panel hanger;

FIG. 7 is a cross-sectional view taken-online 7-7 of FIG. 6;

FIG. 8 :is afragmentary, enlarged, vertical cross-sectional view like thatof FIG. 2'but illustrating a modified lining construction;

FIG. 9 is a front elevational view of one hanger panel taken on the plane of the line9--9 of FIG. 8; and

FIG. 10 is a fragmentary, enlarged cross-sectional view generally like that of FIG. 2 but illustrating a further'modified lining construction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present lining construction can be used in all types-ofelectric furnaces where a resistor element is to be mounted, such as in an electric oven, kiln or other industrial furnace. For convenience of reference, the lining construction is shown and described in connection with a furnace useful in annealing or otherwise .heat treating coils of rod, wire, or the like.

Referring to FIGS. 1 through 5, an electric furnace generally represented at F includes a metal shell 10 open only at its upper end and suitably supported by pedestals 11. The interior and purpose of the furnace F do not form apart of the present invention and therefore are notdescribedin detail.

In *theembodiment illustrated, the open end of shell 10 hasperipherally mounted,cooperating sealing rings 12 and 13 of conventional design. An inner cover 14 suspended from thecover'plate 16 extends into the furnace chamber. Inner cover 14 is a rigid envelope of circular cross-section, closed at its bottom and open at the toptoreceive a support, generally indicated at 15, for

material to be heated in the furnace such as metal coils.

The support 15 includes cover plate '16 from which depend downwardly extending, spaced apart bars 18 supporting at their lower ends a circular grating 17. In

chamber within the inner cover 14.

Referring more particularly to the furnace lining construction of FIG. 1, a linerlayer 23 of fibrous insulating material covers the inner sideof furnace'shell l0 and'is held in place by suitable means including spaced,

headed studs 24 which penetrate the liner layer 23 and are suitably fixed to the shell '10 as by spot welding. The resiliency of fibrous layer 23 enables it to accommodate expansion and contraction of parts, thereby minimizingbreakage or other damage. The insulating layer 23 isspreferably made up of resilient, porous batts of ceramic fibers such as glass, slag, asbestos, and the like.

As shown in FIGS. 2 and 5, the heads 25 of studs 24 are sufficiently spaced from layer 23 to form support means for resistor hanger panels 26. These panels are of generally rectangular outline and are made of electrical insulating material, preferably a hard ceramic material which is mechanically strong and electrically non-conductive at the highest temperatures normally reached in the furnace. As illustrated, each panel 26 is molded in one piece and includes along its back, which contacts insulating liner 23, a series of recessed vertically elongated, undercut cavities 27 and on its exposed front a plurality of projections 28 extending along its upper margin and a plurality of projections 30 extending along its lower margin.

Each cavity 27, of which four are shown in each illustrated panel 26, has an opening 31 (FIGS. 4 and sufficiently large to pass a head 25 of a stud 24, the opening narrowing upwardly to a slot 32 having a width slightly'larger than the diameter of a stud 24. Inwardly past the opening 31, the cavity 27 is of uniform size to receive the entire head 25 in both its open lower and undercut upper ends.- Accordingly, a panel 26 can be mounted on a stud 24 by moving the panel so that head 25 enters the open lower part of cavity 27 through the opening 31 and then seating the panel by moving the same downwardly so that the shank 24 of the stud enters the slot 32 and the head 25 seats in the undercut upper part of cavity 27 behind the retaining wall portion 27' as clearly shown in FIGS. 4 and 5. A panel may be removed by reversing this procedure.

FIGS. 6 and 7 illustrate a modified embodiment in which a panel 33 has a substantially square undercut cavity 34 having an opening 35 which narrows to a slot 36. In this case, a stud 37 has a T-shaped head 38 which enters the cavity 34 at its widest part and then seats in the upper portion of the cavity behind the slot 36.

The projections 28 and 30 on the panels carry and locate anelectrical resistance element such as a ribbon 40. The upper projections 28 have upturned lips 41 to retain the ribbon in place. The lower projections 30 serve to keep the lower loops of the ribbon in place. In this connection, the ribbon 40 may either pass around a projection 30 as seen in FIG. 3 or between two such adjacent projections. The ribbon 40 in sinuous shape extends horizontally from panel to panel. There may be sufficient number of tiers of panels with electrical resistance elements to cover the entire wall of the furnace as represented in FIG. 1. Suitable external connectors'42 are supplied to energize the ribbons 40 in a manner known in the art. As seen in FIG. 2, the panels 26 of one row may serve at least partially to support the panels of the row next above, so that the weight of that row is not entirely carried by studs 24.

FIGS. 8 and 9 illustrate a modified lining construction in which panels do not have cavities to receive the heads of studs but are still adapted for removable mounting against the insulating layer 23. In this embodiment, furnace shell 10 and insulating layer 23 may be the same as previously described, but panels 43 have non-recessed backs which contact the layer 23. Pins 44 penetrate layer 23, are spot welded to the shell 10 like studs 24, and pass outwardly from the layer 23 between horizontally disposed rows of panels 43 as illustrated by FIG. 9. a

Cambered or dished washers 45 are centrally pierced and slotted to form tangs 46 and are pushed inwardly over the pointed ends of the pins 44 until the washers press against panels 43 of two adjacent rows. The form of the locking washers is such that, while they may be easily pushed inwardly over the ends of the pins 44. the washers lock against normal outward movement due to the locking action of the inclined, slotted tangs 46 of the washers. The panels 43 have upper projections 47 and lower projections 48 which mutually support an electrical resistance ribbon, as in the case of the embodiment of FIGS. 2 through 5.

FIG. 10 illustrates still another modification of a removably mounted support for an electrical resistor. In this case, studs 50 penetrate insulating layer 23 and are fixed as by spot welding to shell 10. The outer end of each stud 50 is threaded and has sufficient length to carry a spool 51 which is removably retained in place against layer 23 by a nut 52. An inner flange 53 on the spool 51 seats against the layer 23, while an outer flange 54 retains the electrical resistance ribbon 40 in place. To replace a spool 51 on a bolt 50, it is necessary only to remove the nut 52.

Although the panels have been shown as substantially flat, it is understood that the panels can be curved in any plane to meet diverse needs of installation.

While the foregoing describes several embodiments of the present invention, it is understood that the invention may be practiced in other forms within the scope of the following claims.

Iclaim:

l. A furnace wall construction including a furnace shell, an insulating liner layer supported on said shell, resistor hanger panel fastening studs penetrating said insulating layer and having one end portion secured to said furnace shell and an opposite end portion extending inwardly beyond said insulating layer, a plurality of ceramic resistor hanger panel members removably mounted on said opposite end portions of said fastening studs and held in position thereby, said panel members having heating element supporting projections extending inwardly away from said insulating layer, and an electrical resistance heating element supported on said projections.

2. The furnace wall construction of claim 1 in which said fastening studs have enlarged head means on said opposite end portions, said head means engaging said panel members and retaining same against movement away from said insulating layer.

3. The furnace wall construction of claim 2 in which said panel members have cavities adapted to receive and enclose said head means of said fastening studs.

4. The furnace wall construction of claim 3 in which the cavities in said panel members have openings adapted to pass said head means of said studs and undercut upper portions adapted to receive and retain said head means.

5. The furnace wall construction of claim 1 in which said projections on said panel members are disposed along both the upper and lower marginal portions of the panel members.

6. The furnace wall construction of claim 1 which includes at least two horizontally disposed rows of said panel members, at least one panel member of a lower row contacting at least one panel member of an upper row and aiding in the support of said last-mentioned panel member. 

1. A furnace wall construction including a furnace shell, an insulating liner layer supported on said shell, resistor hanger panel fastening studs penetrating said insulating layer and having one end portion secured to said furnace shell and an opposite end portion extending inwardly beyond said insulating layer, a plurality of ceramic resistor hanger panel members removably mounted on said opposite end portions of said fastening studs and held in position thereby, said panel members having heating element supporting projections extending inwardly away from said insulating layer, and an electrical resistance heating element supported on said projections.
 2. The furnace wall construction of claim 1 in which said fastening studs have enlarged head means on said opposite end portions, said head means engaging said panel members and retaining same against movement away from said insulating layer.
 3. The furnace wall construction of claim 2 in which said panel members have cavities adapted to receive and enclose said head means of said fastening studs.
 4. The furnace wall construction of claim 3 in which the cavities in said panel members have openings adapted to pass said head means of said studs and undercut upper portions adapted to receive and retain said head means.
 5. The furnace wall construction of claim 1 in which said projections on said panel members are disposed along both the upper and lower marginal portions of the panel members.
 6. The furnace wall construction of claim 1 which includes at least two horizontally disposed rows of said panel members, at least one panel member of a lower row contacting at least one panel member of an upper row and aiding in the support of said last-mentioned panel member. 